A male has one X and one Y chromosomes which means half the male gametes i.e. sperms have X and the other half will have Y chromosome, whereas in females both the chromosomes are X thus all the females gametes will have one X chromosome. In humans, the sex of the child depends on what happens at fertilization. If Y chromosome is inherited by the offspring then it will surely be a male because the child will have XY combination of sex chromosomes.
